Polypropylene fibers have many attractive characteristics for use in a wide variety of fabrics, including upholstery fabrics. Along with its many advantages, however, polypropylene fabric, in the past, has suffered a significant disadvantage in the area of its very high heat of combustion, which has rendered very difficult the matter of meeting fire retardancy standards imposed by the National Fire Protection Association (NFPA).
The process of the before mentioned Davis et al. U.S. Pat. No. 4,863,764 represents a major advance in the ability to impart appropriate levels of fire retardancy to polypropylene fabrics without seriously degrading the characteristics of the fabric and without adding excessive cost to the manufacturing process. The disclosure of the Davis et al. U.S. Pat. No. 4,863,764 is incorporated herein by reference and made a part hereof, and reference to said patent is recommended for full details of the process described therein. In general, however, the disclosed process involves the application of a bromochlorinated paraffin/antimony oxide composition to the fibers or to the fabric in amounts of about 2-15% dry weight, relative to the polypropylene fibers. Where seam strength is a factor, the fire retardant composition is mixed with a binder, desirably an acrylic latex.
Because of the characteristics of the fire retardant composition, fabrics treated according to the process of the Davis et al. U.S. Pat. No. 4,863,764 sometimes have a characteristic oily feel, due to the fact that the bromochlorinated paraffin composition, which is applied by the process, is a basically oily composition. The oily feel of the fabric is not particularly desirable, and it can result in an increased retention of soil o the surface of the fabric.
In accordance with the present invention, polypropylene fabrics are treated with the fire retardant composition disclosed in the before mentioned Davis et al. U.S. Pat. No. 4,863,764 by means of a back coating procedure, combined with the back coating operation heretofore commonly performed for the purpose of effecting improvement in seam strength. Significant advantages are derived from the new process in that the exceptionally effective fire retardancy of the before mentioned Davis et al. patent can be imparted to the fabric while at the same time realizing important improvements in the characteristics of the processed fabric. By using the new procedure, the feel of the surface of the fabric is improved, any tendency for soil retention is reduced, and improvements are realized in the seam strength cf the fabric. In addition, significant economies are derived from the fact that the fire retardant material is applied in conjunction with and as part of the customary back coating of the fabric, normally carried out only for seam strength improvement, so that separate operations are not required.
In accordance with the present invention, a fire retardant composition, prepared in general accordance with the teachings of the Davis et al. U.S. Pat. No. 4,863,764, also incorporates an effective amount of a hydrated refractory or earth metals, preferably aluminum oxide trihydrate, in the form of a fine powder. The fire retardant mixture is adsorbed on the surface of the hydrated powder and the final composition is then applied to the back surface of the upholstery fabric via a back coating operation.
For a more complete understanding of the above and other features and advantages of the invention, reference should be made to the following detailed description of a preferred embodiment.